1. Field of the Invention
Water-in-Oil emulsions resulting from the water wash of crude oils are broken using an oxyalkylated cardanol-phenolic-aldehyde resin.
The desalting of crude oil is a process in which salt and clay or other suspended solids that are present in crude oil are removed. Salts and suspended solids occur in crude oil as a result of natural contamination in the ground or occur as the result of contamination during transport. Solids and salts present in the crude oil must be removed prior to distillation since salt present in the oil may hydrolyze during processing giving HCl which can cause severe corrosion of equipment or which may lead to the plugging of process equipment due to the formation of insoluble salts. Salts and solids remaining in the distillation bottoms may cause problems in storage or during combustion of residual fuel oil. Salts and solids are removed from crude oil by washing it with water. This invention is directed to a method for resolving emulsions formed from the washing of crude oils using certain oxyalkylated cardanol-phenolic-aldehyde resins. Solids and salts settle from the wash water and tend to form emulsions which are often difficult to break especially from so called heavy crudes. The wash water is typically separated with heat, electrostatic precipitation, and various chemical additives.
It is an object of this invention to provide a superior chemical treatment for the resolution of emulsions formed as a result of washing crude oils with water.
It is a further object of the invention to provide a process for the resolution of water-in-oil emulsions formed from the water wash of crude oils using as chemical additives, certain oxyalkylated-cardanol-alkylphenol-aldehyde resins. Further additional objects will become apparent as my invention is described below.
2. Summary of the Invention
We have discovered that certain phenolic resins prepared by the base catalyzed condensation of cardanol, a para-alkyl phenol, and an aldehyde are superior chemical additives in resolving emulsions formed from the water washing of crude oils. The particular resins employed are described in copending application Ser. No. 08/105,025, filing date Aug. 10, 1993 which is hereinafter incorporated by reference into this specification.
The oxyalkylated-phenol-formaldehyde resins which are useful in the practice of this invention are those prepared by the base catalyzed condensation of cardanol, a para-alkyl phenol, and an aldehyde followed by reaction with an alkylene oxide or mixture thereof. An explanation of the synthesis, properties, and use of such resins can be found in the work of DeGroote et al. See, U.S. Pat. Nos. 2,524,890; 2,524,891; and 2,524,892 all of which are hereinafter incorporated by reference. DeGroote teaches the use as an oil emulsion breaker of ethoxylated derivatives of phenolic resins made by the condensation of formaldehyde, cardanol (a meta-substituted phenol derived from the shells of cashew nuts); and various ortho- and para-substituted phenols. This condensation may be either acid or base catalyzed, producing resins having at least 3 and up to 7 phenolic units whose molecular weight increases by subjecting the reaction to vacuum distillation and heating conditions. DeGroote reports preparation of phenolic resins having up to 20 phenolic units, but expresses a preference and claims for emulsion breaking purposes resins having fewer than seven phenolic groups per molecule, prepared in an acid catalyzed condensation.
As noted by DeGroote, emulsion breakers for crude oil can be introduced at various points along the chain of oil production. Typically, demulsification is conducted via heater treater vessels in which the oil is separated in the presence of heat and emulsion breaker. While the subject invention is directed to emulsion breaking, it is not directed to the demulsification of crude oil, but emulsions resulting from the water wash of crude oils to remove salts and solids from crude oil. Emulsions of this type typically contain small amounts of water (5%) as compared to naturally occurring crude oil emulsions.
Various derivatives of phenolic resins have found use as emulsion breakers. Most commonly, the resins are oxyalkylated to increase their molecular weight and modify their solubility or hydrophilic/lipophilic balance.
What I believe is not known in the art, for which I seek protection and exclusivity by this Letters Patent, is the use of certain oxyalkylated cardanol-alkylphenol-aldehyde resins (and their derivatives) having a high molecular weight (8,000-40,000) and phenolic moieties (40-100) as additives for the demulsification of water-in-oil emulsions formed from the water wash used in desalter units to remove soluble salts, suspended solids and the like from crude oil.
This invention begins with the preparation of a novel series of phenolic resins by the base catalyzed condensation of cardanol, a para-alkyl phenol, and an aldehyde. These compounds and their synthesis is described in commonly assigned pending application, Ser. No. 08/105,025 filed Aug. 10, 1993 which is hereinafter incorporated by reference. Superior results have been obtained with the hydroxide catalyzed condensation of cardanol, p-nonylphenol, and formaldehyde. By such processes, I have prepared phenolic resins having a higher molecular weight with a branched structure and a greater number of phenolic units per molecule than those of the prior art.
As with the phenolic resins of the prior art, derivatives may be prepared from the phenolic resins of this invention. Thus, adducts have been prepared using ethylene oxide, propylene oxide, 1-2 butylene oxide, and mixed oxides wherein the oxide accounts for between 20 and 80 weight percent of the resulting adduct. The oxyalkylated base catalyzed cardanolic resins useful in the subject invention typically are condensed with 1 to 40 mole of alkylene oxide per mole of resin and preferably 1 to 30 moles of alkylene oxide per mole of resin. In a preferred embodiment of this invention, 1 to 20 moles of alkylene oxide are condensed per mole of resin.
Surfactants prepared from these high molecular weight oxyalkylated phenolic resins have been successfully employed to break emulsions formed as a result of the refinery desalting process for removing salt and suspended solids from crude oils. It is common practice in the breaking of water-in-oil emulsions of the type formed from the aqueous wash of crude oil to mix together various surfactants, often of different composition, to obtain a blend that exhibits superior demulsification properties when applied to desalting units using crude oils of various origins. Bottle testing using the novel desalting cardanolic oxyalkylate additives of this invention have shown better performance than those blends which lack the cardanolic resins of this invention.